On 06/21/2018 11:25 PM, Jason Gunthorpe wrote:
On Thu, Jun 21, 2018 at 04:59:55PM -0400, Stefan Berger wrote:
On 06/21/2018 04:53 PM, Mimi Zohar wrote:
On Wed, 2018-06-20 at 16:42 -0400, Stefan Berger wrote:
Rather than accessing the TPM functions using a NULL pointer, which
causes a lookup for a suitable chip every time, get a hold of a tpm_chip
and access the TPM functions using this chip. We call the tpm_chip
ima_tpm_chip and protect it, once initialization is done, using a
rw_semaphore called ima_tpm_chip_lock.
Use ima_shutdown to release the tpm_chip.
Signed-off-by: Stefan Berger <stefanb@xxxxxxxxxxxxxxxxxx>
security/integrity/ima/ima.h | 3 +++
security/integrity/ima/ima_crypto.c | 12 ++++++++++--
security/integrity/ima/ima_init.c | 19 ++++++++++++-------
security/integrity/ima/ima_queue.c | 7 +++++--
4 files changed, 30 insertions(+), 11 deletions(-)
diff --git a/security/integrity/ima/ima.h b/security/integrity/ima/ima.h
index 354bb5716ce3..53a88d578ca5 100644
+++ b/security/integrity/ima/ima.h
@@ -24,6 +24,7 @@
#include <linux/hash.h>
#include <linux/tpm.h>
#include <linux/audit.h>
+#include <linux/rwsem.h>
#include <crypto/hash_info.h>
#include "../integrity.h"
@@ -56,6 +57,8 @@ extern int ima_policy_flag;
extern int ima_used_chip;
extern int ima_hash_algo;
extern int ima_appraise;
+extern struct rw_semaphore ima_tpm_chip_lock;
+extern struct tpm_chip *ima_tpm_chip;
ima_add_templatE_entry() synchronizes appending a measurement to the
measurement list and extending the TPM by taking a lock. Do we really
need to introduce another lock?
This lock protects the ima_tpm_chip from going from != NULL to NULL in the
ima_shutdown function. Basically, a global pointer accessed by concurrent
threads should be protected if its value can change. However, in this case
ima_shutdown would be called so late that there shouldn't be concurrency
anymore. Though, I found it better to protect it. Maybe someone else has an
opinion?
Why have a shutdown block? There is no harm in holding a kref if the
machine is shutting down.
Looking around at other drivers' usage of the reboot notifier, I find
other drivers as well that use spinlocks or mutexes during the shutdown.
Besides that, we do have the shutdown block already when device_shutdown
calls tpm_class_shutdown() and we get the ops_sem.
Stefan
Jason
